Subaru timing belt tensioners, my nemesis
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- Опубліковано 28 січ 2023
- I have had plenty of tensioners fail, causing timing belt breakage and subsequent engine damage. It can’t be this hard, what am I doing wrong? I am using all Japanese parts; perhaps I need to “bleed” the tensioner for success.
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I was a loader at UPS during college. Unless they've changed their rules to account for this somehow, there is no guarantee that your package is going to be shipped in a given orientation. You can put arrows on all sides of the box and the label on the 'top', and it'll be more likely, but there's a good chunk of loaders that DGAF about your package. So, they sit in the semi trailer however they're oriented. Then, the unloaders at the next location are likely much more careless. Once it's in the system, though, it moves pretty fast for the most part. Just wanted to put that out there.
Fun bonus fact: I lived in central Japan for like 9 years and, at one point, was a delivery driver for a parts supplier for a lot of automotive-related factories around Hamamatsu City (where Soichiro Honda grew up). Dealt with Aisin, NSK bearings, Showa shocks, Showa leather, Enkei wheels, and a number of other suppliers commonly-used parts.
Your honesty about doing it wrong is refreshing... no ego. That's rare. I've been working on cars for 35 years. My list of things I have screwed up is very long. Nothing permanently sets in to do something the right way like doing it the wrong way first. - I bleed them five times. And, don't let it fall over after (mistake I've made)
Thank you for such an encouraging comment!
FITTED HUNDREDS AND NEVER EVER HAD ONE FAIL YOU CANT GO WRONG
Thanks for posting this. My Haynes manual (it's not my car) states the tensioner must be compressed vertically. I went looking for the reason. Quirky things these EJ engines.
Great work friend 👏 👍
Thanks for the insight.
Keep wrenching
I stripped the 10mm bolt for the tensioner, no helicoil for me, i drilled out the remaining thread and with a longer bolt , threads out and a washer and nylock nut pulled it up to a snug pivot point ,what could go wrong? Already 50000km,
Just had a belt slip several teeth on the right cam after a head gasket repair Had a belt guard in place. I reused the tensioner and belt since they had less than 10K miles. I did recompress the tensioner a couple times and stored it on its side for a month. Guess this explains my dilemma why the belt slipped so much and I did hear the “knock” but didn’t recognize what it was. I do have valve damage so get to do it all over again. I don’t think my cam would have hung up most likely thinking tensioner especially hearing the knock, My belt slipped at idle in the garage so thankfully wasn’t stranded.
Sorry about your fortune. Tensioners seem so finicky. It’s almost like it’s vudu… real stupid
Try not to overthink this. I will give you a few suggestions but first let me say I have not had many tensioner problems. I always use oem or aisin as you said you do also. I do not reuse a tensioner that is wet outside the seal. I use dayco timing belts. When I install my tensioner (lastly) my 2 idler and 1 gear pulley are all backed off one thread so they have some wobble. After all slack is between L side cam gear and crankshaft gear I install tensioner almost effortlessly lining up with the threaded hole. After tightening down all 4 loose bolts I pull the pin and gently pry the tensioner slightly to get the belt even tighter than just pulling the pin did. Hope this helps. Oh, when you have the tensioner in the vice very slowly crank. It should always be easy to turn. If it’s difficult to crank in you are working it in to quickly and this can most definitely compromise the integrity. I do not do a bleeding sequence. I do hundreds a year. If I had to guess I’d say you are having issues with quality timing belts. If a timing belt breaks it’s almost got to be belt failure. I highly doubt it’s a tensioner issue
Thank you for that feedback Subeez. Let me ask you this, why might I be having such trouble with them failing? Could it be the way I’m having them shipped? Small parcels jostled around and shaken upside down? The Aisin kits tend to ship right side up in the larger box, those have been pretty good to me so far. Tensioners that I’ve bought individually online have been more trouble.
@@stvnswld the only tensioners I’ve ever had fail on me are the ones that say made in Canada. I think they come in the dayco timing kit. I don’t touch those. I usually reuse factory oem tensioners as long as they aren’t wet. I believe your issue may be in the timing belt but just my guess.
@@bRob1077 thanks again for the feedback
@@bRob1077sorry for responding so late, by wet do you mean leaking from the piston? Or somewhere else?
Im going to do a timing belt soon and was curious what you look for. Mine should have been replaced 10k miles ago, so i was just going to check it out while replacing the belt and water pump
It was originally installed 5000 miles ago with a Japanese kit from Rockauto.
Over 3 minutes is a bit excessive. The instructions in my kit said no faster then 1 minute up or down. In service, the tensioner is going to see activation a lot faster then that. Pretty much instantious as your hit the gas the belt on that side will slacken, and tensioner will respond just as fast. Take foot off the gas and it will tighten just as fast, requiring the tensioner to respond just as fast. The issue was, you just were not bleeding the tensioner. I don't care which type of box it is in, it will end up being spun around in all directions during shaping. Bleeding is a must!
Just adding my .02, ive been fixing subarus at my shop for 13 years never had a failed tensioner or belt comeback, ive used subaru, gates, and aisin kits, i prefer subaru or aisin and wont use gates anymore. i have probably installed 20-30 timing kits in my life on subarus. Now if were talking about a cloyes timing kit on a gm 3.6 i had one fail in 4000 miles, the oiling squirter hole in one tensioner was drilled in the wrong location, chain went dry and slack. Have a great day.
I recently had a conversation with a Subaru specialist several hours away from me, and he suggested that the cam might be hanging up in the journal enough to tighten the belt and overload the tensioner. He has seen it quite a few times. The remedy is a new cylinder head. I thought that was a real interesting hypothesis.
I heard you mention Gates. Gates has literally become junk. The tensioner you have in the vise, definitely looks Chinese. The bearing might say Japan, that's the only part that came from Japan. I started buying Subaru's in 2003. I have never had an issue with timing components until Gates stopped using Japanese parts. I had a Gates timing set on my 06 Outback. Less than 5,000 miles, the bearing seals started slinging grease. If that tensioner in the vise doesn't say Japan, it is definitely Chinese.
The one in the vise was in an NTN package. The ones I’ve gotten directly from Subaru are identical to this one in the vise.
Did you "bleed" out the tensioners prior to installing it ? What brand are you currently using ? I used a gates kit years ago , that failed after 40,000 miles . It was the tensioner that failed .
I’ve been asking around to dealers and mechanics. They all claim that you can pull the pin and go. There is no bleeding to be done. So the last time I used a factory Subaru one that I purchased at the dealership and did not bleed it at all.
I just got into Subies, really like how they drive but haven't had a failure yet. Was planning to buy an Aisin kit and do a timing belt replacement job in the next couple of weeks. Now you have me worried I will get a borked tensioner. Ugh.
Sorry. Some guys are telling me I’m making it too complicated and you just put it together and go. I am still looking for the answer. Read through some comments I’ve received from professionals. Also, add a belt guard over the crankshaft sprocket. They’re 15 bucks and it will keep the belt from jumping off even if your tensioner fails!
Aisens are the best kit for a subie
My understanding is Aisin and Subaru are the same. Some people bleed them, some say you cant bleed them. I didn't.
I may have missed it if you mentioned it, but has anyone had this issue with the old style tensioner? It lays horizontally when bolted in place, and they seem to last forever. They can be swapped in place of the newer style if you replace the mounting bracket. Maybe a solution to this problem?
I have pursued this path as well! I think it would be a tremendous alternative to this style tensioner. I have read that they are far more reliable. I didn’t have very good success finding the old style bracket, but there is a company out there that offers That bracket along with the tensioner assembly, but it costs quite a bit of money
@@stvnswld I am doing a belt/water pump/pulley replacement on my 95 2.2 right now. Old style tensioner is in perfect condition, but will be replaced with the new "old style" tensioner that came in my Aisin kit. I will compress and keep that old tensioner in the event I have the opportunity to use it in the future.
I guess the market for OG Subaru "old style" tensioner brackets just got a little more lucrative.
You have great integrity. They really need to put better install information on the product. Also, if the tensioner is that sensitive to orientation during shipping...I call that a design flaw. Apparently, the proper tension and function needs to be verified before installation...weird.
Thanks for the reply. I’ve been experimenting and am finding that once installed, one should pry the belt down with a bar to allow the tensioner to extend ever so slightly. I think my problem has been that the tensioner is allowed to move unless the piston is pushed out more than pinned position.
@@stvnswld Interesting. That makes sense to allow the tensioner to come out a bit more for better belt tension.
Hi is it possible to remove and fit just an aftermarket belt guard to a timing belt already fitted? My belt is only three years old and I would like to upgrade the guard for piece of mind.
Yes, you can add a belt guard pretty easily once you remove the timing cover. I’ve done that several times.
@@stvnswld Awesome thanks for the reply 👍
its crazy you can watch a 10 min video on a conclusion of years of experience
Doing my own and thinking of adding a hard stop. Screw from top of bracket to limit the amount the tensioner can back off. Or a split set collar spacer on the tensioner piston if it can be fitted after tensioned...🤔
I have started using belt guards like the manual trans cars have. Over the crank pulley. I have also done what you’re suggesting! I notch a washer that slide in around the pin and then I put a couple of rubber washers around the pin also and silicone them together. To limit the amount of travel upwards the tensioner can go, great thinking. Necessity is the mother of invention, my uncle always says!
Had a cat in the engine..timing belt jumped 4 teeth..long story.. reset it today..put the tensioner in a horizontal vice and slowly compressed. Put the pin in and reinstalled everything. Car runs great like nothing happened…but…think I will be ok having compressed it horizontally? Feel like I dodged a bullet with a 4 tooth jump…think I will be ok on this tensioner? It’s all put back together and complete. Thoughts are appreciated.
If it jumped once because the tensioner went soft, it will more than likely do it again. I don’t think it’s safe to reuse
@@stvnswld it only had 5 k miles on the timing set. a cat got in the belts..that made the crank skip 4 teeth behind as the accessory belts were shredding. My question in valves resetting the tensioner horizontally in a vise vs vertical. It’s all put back together when I saw your channel saying to re load the tensioner vertically.
@@louisross9691 It’s tough to say, really. I’m not saying it’s going to fail for certain because you did it that way. All of the procedures I have read say it should be vertical to avoid air being introduced into the wrong places inside the tensioner. I was thinking the tensioner is what failed, my mistake. Poor cat, yikes 😬 Since it’s together and runs great, I’d run it. Make sure you listen for the dreaded tensioner knocking noise though, sometimes you can catch it before it causes the timing belt to jump and break. I have a new rule, I always instal a belt guard over the crank pulley so if the tensioner does fail, I have time to catch it and fix it because it keeps the belt from jumping teeth on the crank. My latest video shows the guard I’m talking about.
Yeah poor cat for sure, it was ugly. Thank you so much. I think that’s great advice...I’ll keep an ear out for that tensioner noise. Maybe listen with a stethoscope once in awhile. The reason I looked it up again (after it was all buttoned up) is because when I pulled the grenade pin it had almost no pressure to remove it. Maybe should have stopped here. I really appreciate your time and your channel. Thanks again and well done !@@stvnswld
@@louisross9691 glad to help! One commenter wrote that once he pulls the grenade pin he pries down on the tensioner very gently to give it an extra tad bit of tension, especially if the tensioner doesn’t adjust much after the pin is pulled. I tried that on my last one and like how it felt as well. Best of luck with the Subie, I pray it holds together well for you. Pretty wild when they jump 4 teeth and not blow up. God is merciful, I suppose!
Man, I’m getting a “knocking” noise that I believe to be the tensioner. I was gonna tackle it myself but now I’m a bit worried. Any feedback since you started the slow bleeding process? I’ve read mixed reviews about Gates.
Since posting this video, I have done as the professionals recommend which is pull the pin and go. The dealership says you don’t need to bleed anything, you put it on and go. Every car now gets a belt guard. If you watch some of my later videos where I did timing on my personal cars I have begun experimenting with different brands, but have always added a belt guard just in case the tensioner fails. That way the belt won’t jump off the crank pulley And mess up your engine. Last weekend I replaced tensioner on my friends 2005 outback. He went to the Subaru dealership and bought it right off the shelf. Within two days it started hammering. I told him to take it back to the dealership and try to get some warranty from it. I’m just glad that we had a Belt guard on to keep things from getting out of hand. I don’t trust any tensioner anymore. Belt guard belt guard belt guard, it’s insurance against tensioner failure. Sorry if this reply became a little more than what you anticipated 🤪
@@stvnswld ok. I think what you’re saying is get a belt guard. Looks like I’m gonna put it off another weekend until o get a belt guard. Thanks for the info. I just found your channel so I’ll start digging around because I’m slowly updating my 04 after some neglect. Thanks again.
I had that. Threads for tensioner stripped. Buy the plate that holds the tensioner
@@scottloutner5253 I’m actually gonna tow it to a shop next week since the timing components are under warranty when they replaced it. I’ll mention the bracket if they do indeed come back with timing problems. Thanks.
I had a overheating engine problem in my 2009 with 330,000 km forester naturally aspirated engine. Shows any little engine oil leake in the floor after drive let say 20 drops and leake stops when not driven. In effort to fix leake i used blue devil solution adding in oil and coolant, change rad, coolant, termostat, temp sensor, check for gasket leake in coolant was negative.
Never found dhe reason of overheat engine.
I doubt that leake was from combustion cilinder to engine oil through head gasket breaker.
Somebody have any idea what reason might be.
Aftermarket Thermostat ?
@@DKSE123 hi there, I don't belive was thermostat bcs I put first aftermarket and as heating continued I put from subaru diler.
I sold the car for junk only bcs couldn't fix overheating problem.
Car was so good other than overheat.
And more I am curious what reason for overheating. I Changed sensor, radiator, coolant, thermostat from diler, Enginee oil
It's important to change the antifreeze on schedule. Subaru recommends every 30,000 miles. I recently tore down an engine and after removing the cylinder heads, I discovered a large amount of white crud in the water jackets around the cylinders. In time as this problem progressed this would have caused overheating. An all aluminum engine such as the boxer needs antifreeze changed sooner than we would normally consider after running cast iron blocks and heads all our lives.
Bought a 03 OBW from someone who DIY'd head gaskets and timing belt. He must have not known what a torque wrench is because he stripped out the tensioner mount, which fell off two months later shredding my timing belt. Forced me to learn how to tear down heads and replace valves. What a headache!
I feel you! Quite the job indeed.
Do you have a part or source of where you're finding your belt guards? I've got the 3 and 4 cyl phantom misfire going on above 4k rpm. I've swapped every part except the reluctor gear, which I have ordered. Figured as long as I'm in there I would put on a guard for added security. Thanks
I get them on eBay. Usually they’re about $15 each. Another thing to try would be dumping a can of sea foam in the fuel tank. I have a ‘13 forester that was coding for “random misfire”, P0300 over 3500-4000 rpm. It hadn’t been run in quite some time, so I’m thinking the injectors weren’t flowing well over 3500 Rpm. After putting about 20 miles on, I can’t get the code to come back.
@@stvnswldI have another 09 forester as my daily, so I swapped the entire intake and wiring harness over from that car to the one with issue, and it didn't take care of my problem. I'm just about at a loss as to what it can be if the reluctor doesn't take care of it
@@prestonbear8981 I get that. I’ve been there! Misfires are tricky devils. I would try the seafoam, I know it’s like mechanic in a can but it’s worth a shot. Put it in the fuel tank and run it.
@@stvnswld I will give it a shot although I don't that's the problem because the injectors were part of the intake swap. I had the codes before I put a new short block in it as well. The old one had a rod knock so it needed to be done and just thought the misfire may clear up with the new one, but no such luck yet. I swapped the crank sensor with the other car as well, and put on a new Aisin timing kit. Heads were gone thru as well.
@@prestonbear8981 you’ve probably already tried a knock sensor. I seem to remember a guy having a misfire and it was a bad variable valve solenoid. I don’t know how to test those though.
ordering an iag timing belt kit for my jdm ej205. hope it works
You’ll probably be alright. Make sure to let the tensioner sit in the upright position for a day before install.
Are you parts Japan mainland ?
We don't use Gates as found many parts not Japan mainland factory sourced ,
Aisin is good kit, personally I prefer OEM sourced idlers/ tensioner all clearly marked Japan made and use Mitsuboshi belts .
Notes I seen on air in tensioner refer to only needing store in correct orientation for 24hrs before use.
Do/done hundreds of these and don't see repeat tensioner problems .
Thank you for the input! I am finding that the tensioners are failing because the camshafts are hanging up into the head journals and over tensioning the belt. That’s what is causing a lot of the failures.
When you compress that you have to do it very slowly over a long period of time. You can't just force it back quickly or you can make it fail quicker.
That is correct
Buy the IAG V2 Competition Series EJ timing belt tensioner. It's only $525. Cheaper than engine work.
I’ve looked into alternative tensioners like the IAG. I honestly like the design…a lot. I’ve tried to find brackets for the mounting of the old style tensioner, but Subaru has discontinued that design. Which is a bummer, because that style wasn’t as prone to failure as the current one. I have had a lot better success as of late, made some changes in terms of suppliers. Also I’ve added belt guards to ensure the belt doesn’t jump time and break if the tensioner does fail. That’s SOP for me now, every car gets a guard.
MrSubaru says it's a new recommended procedure now to bleed the tensioners.
Can you link me to that video? I would like to watch it!
@@stvnswld ua-cam.com/video/BJg9hhReU3E/v-deo.html
@@stvnswld ua-cam.com/video/BJg9hhReU3E/v-deo.html
I got an old style piston tensioner mounting bracket so ima switch over to that
Wish I had one!!
I don't know how many subaru timing belts I've done at my shop, but I have never had a tensioner failure. I do nothing special, other than install it right out of the box. Gates come laying on their sides, in the kits. Not sure what your issue was.
I think the cam hangs up in the journal and tightens the belt, causing an overload on the tensioner. Something I’ve learned since posting this vid
@@stvnswld i have seen that. Actually seens the cams snap in half from it.
@@Arcade-fix what causes that kind of damage? Dirty oil or lack of oil pressure? To cause the cams to wear and potentially break?
How, could air be introduced when theyre pinned as a air free unit. No movement
I guess I don’t know how, technically. If there couldn’t be air introduced somehow I don’t know why Gates would include a recommended bleeding procedure 🤷♂️
@@stvnswld
When it comes to timing belts don't trust gates info or parts ...
Pine Hollow Auto Diagnostic (Ivan) always used a Gates “kit” with all the idlers and pulleys with no problem, UNTIL NOW! gates has starting to use Chinese made bearings which he caught even though the Gates kits specifically states that each component is made in Japan. He called Gates and they were surprised also and gave him the runaround. He also called Rock Auto telling them of this and reluctantly they were sending him a refund although the bags were opened. Ivan will NOT use any Chinese pulleys on the Subaru with fear that they will fail and destroy the engine. His only option is going to OEM.
That wasn't 'now' it was like six years ago. They still sell a kit which is supposed to contain Japanese parts which has an 'N' at the end of the part number (it is on Rock Auto but I haven't seen it many other places). However if you get a Gates kit which includes waterpump then the waterpump might still be Chinese (from what I have read).
Hi i ordered a Gates kit which was in Ireland and after looking at Pine Hollow{great guy} i asked them to open kit before i purchased and they confirmed must of the stuff was marked made in China. buyer beware
This is so weird. Having a tensioner from a gates kit just absolutely demolish my impreza a week ago I cannot understand how this can be a thing. Didn't used to be a thing I'm quite sure??? There was no bulletin in the tensioner I put on my old forester xt. The bleeding process is new. I think it's likely the manufacturer has a stop gap they hope works. They should send a force gauge because I am sure my vise doesn't regulate itself under 66 lbs. Sorry for the vent, but this crap tensioner stuff went from an unacceptably difficult head gasket replacement on a 2011 car to a nerve racking engine rebuild when the valves and cam shafts were trashed.
I totally agree. I’ve asked so many people about this issue. Pull the pin and go, is what the Subaru techs and everyone else tells me. I’ve had repeat failures on the same car even! It shouldn’t be so complicated, right?
I’m also having issues I replace the tensioner and it only lasted about 40 miles
Since posting, I have had success without bleeding tensioners. I have changed my ordering methods and have stuck to complete kits. I have primarily used Aisin, but experimented on my own car with a Gates kit. When I install everything and pull the grenade pin, I pry down slightly to extend the tensioner pin and put some extra tension on the belt. I have found this to be a good step. Also, I have begun to instal belt guards over the crank pulley on every single car I do timing on. I show that on my forester video.
PHASE I tensioner ftw. That said man that sucks
Thanks for the comment. Is there anything else out there other than the high dollar IAG setup? Subaru doesn’t make the old bracket anymore.
@@stvnswld I went with a junkyard bracket and laser cut my own added tensioner arm to use the sti/wrx idler. Pm me if you need the dxf, you can send it to any laser/plasma cut service of your choice. I also added helicoils to the bracket and replaced the bolts with 12.9 hardware
All the cheep ones tell you to straight up do the 3 cycle bleeding process cause they can't be sure the storage/shipping angle.
Its not voodoo, unless you don't know how a shock works. same shit can happen to a shock but due to there longer travel they are effectively self bleeding.
in short you have a sealed, pressurized cylinder with a piston, the piston has a metering orifice that determines how fast the oil can move from one side to the other, when the tensioner isn't stored vertical when in its compressed grenade pin state, the pressurized nitrogen can end up on the underside of the piston, and when installed its going to basically foam up on startup under, above or on both sides of the piston eliminating most if not all dampening ability, results are well you know.
If you apply too much pressure, that metering orifice cant keep up and the pressure can blow out the rings on the piston absolutely killing the unit.
I'v always used a C clamp on used ones and just applied a steady just enough to compress pressure, think pinky finger on a 3 inch bar tightening the clamp(kinda like the second hand method you mentioned) stopping if i feel the resistance build too quick. A table vice doesn't have the same degree of tactile feedback in my experience.
Fist few times I think I just did 1/2 turn at a time every 5-10 sec, but I'd immediately stop if i felt the resistance come up before completing the 1/2 turn, before waiting 10-15 sec and continuing.
The saying goes "There is more then one way to skin a cat."
That all said, I haven't bought a new tensioner in ~10 years so I cant speak to current quality of them.
I hope this helps you in someway and wish you luck going forward.
Thanks for the reply! Your explanation makes sense. When I bleed them in the vice, I like to feel the tightness increase as I crank, maybe I should slow down even more.
Also, do you have any thoughts on the units that I’ve installed that work fine for 5-10,000 miles and then allow the belt to slack and break? I would think if it’s tight right away, it would be good for the long haul, but that’s not my experience. Please advise. Again, I appreciate your feedback.
If your feeling the resistance build absolutely go a bit slower, to put it another way I ride the wave of I can feel some resistance that is definitely coming from the oil dampener vs spring pressure and clamp/vise drag, but I'm never forcing it.
Going slower never hurts.
Could be bad stock, could have been assembled with bad stock, casing/manufacturing defect, ya sucks if the case.
Seeing as your belt straight up snapped without any warning sign, I suspect you might not have the 13145AA021 stock timing belt guide on above your crank(or its not installed at the correct gap), they used to be stock on every single engine, but bean counters had there way at some point, there are also guides for the cams (dual cam heads at lest) , but no ware as important as the crank one. There are so many videos of people with literally bouncing dead tensioners (ya the spring is still there but 0 dampening), and a engine knock sorta sound, and its almost always the older modal Subarus (still interference) that you find these dead flopping tensioners on yet they didn't blow a motor before the tensioner started sounding like rod/engine knock/piston slap.
O and driving habits have a significant part when it comes to the teeth skipping, the more aggressive one drives, the more likely to skip teeth on a lose tensioner in general.
If not bled, I can see one with a minimum amount of trapped air, after the timing belt settles in and starts stretching a bit, that it could then slowly work in more air and foam till failure.
BTW, generally what happens is the tensioner fails, the crank skips more then I think 3 or 4 teeth(probably more, been a while), and its the interference of the valves that do the belt snapping.
I wouldn't be surprised if Subaru removed the timing belt guide to sell more short blocks since planed obsolescence is in full swing in most manufacturing.
@@TheLoiteringKid wow, that’s great information! I have heard that dreaded knocking sound and shut cars off before damage occurred, but many I’ve repaired haven’t been so lucky. I think along with bleeding the tensioners properly, I will start installing the guide over the crank pulley, even on the automatic transmission cars. All of the belt failures for me have been clean breaks. So interesting to hear the cause of the clean break being the skipping of teeth and valve damage FIRST. Thank you for finding my video and taking the time to make these comments. This is why I like UA-cam.
If you have em use em, there is no logical reason to leave them out knowing what you know now ;). if you don't have one laying around, is ~10$ worth the possibility of saving you block/heads/pistons? I think so, and most agree on that.
Its more the snapped without warning then just snapped that I suspect that's how it went down, again harking back to I'v seen countless videos of dead tensioners and perfectly running motors still going, those belts don't just snap, wear away? sure, I'v seen video of a Subaru running on 1/3 of a belt (width wise, still don't know how), just 2/3's the belt worn away completely.
To snap a timing belt (especially the good stuff, ever try to cut one to make a strap wrench cam holder? they stout) you generally need mechanical damage or a hell of a shock load, it never sees that shock in standard operation, the closest you could get to that kind of shock load is with a manual, and being a jackass, even then I'd bet your skip teeth before snapping a belt, but skipping teeth leads to well, you know at this point. That's not to say its impossible to snap one otherwise, but in my experience that is how it goes down.
As I recall the autos were the first to loose the belt guide, subaru saved ~$10 a car, and introduced a failure mod that likely wouldn't happen in warranty that can kill the entire block win win for them.
I'm no expert but I'v helped build more then a few subarus as my friend's assistant, who built EJ motors and spliced harnesses for the drag strip/pikes peek as a side job(his not mine, I got payed in beer >=) for a few years.
So let me ask you this, the techs at Subaru say “pull the pin and go”, can it be that easy? Would it help if I let the tensioner set upright for a long period of time before install? Will the air/oil equal out? Or must I bleed it if there is any doubt as to how it was jostled in shipment? I bought one from the Subaru dealership last week and simply pulled the pin this time (also installed a belt guard). This tensioner this has me questioning everything I’ve ever known, sadly.